1. Field of the Invention
The invention relates to a pressure indicator, more particularly to a tire pressure indicator which is provided with a light device so as to facilitate the connection of the tire pressure indicator to the inflating valve member of a tire and to facilitate the viewing of the tire pressure reading under poor lighting conditions.
2. Description of the Related Art
A conventional tire pressure indicator comprises a hollow elongated casing having a first end, which is adapted to be connected to the inflating valve member of a tire so as to open the inflating valve member, and a second end having a central hole formed therethrough. A piston member is movably provided inside the casing and has a base portion which is in tight contact with an interior wall of the casing. A pressure indicating stick or rod, which projects from the base portion of the piston member, extends out of the casing via the central hole at the second end of the latter. A biasing member is provided between the base portion of the piston member and the second end of the casing.
When the casing is attached to the inflating valve member, air pressure from the tire pushes the piston member to move toward the second end of the casing. The biasing member is compressed and the pressure indicating stick extends through the second end of the casing by a length corresponding to the pressure inside the tire.
The tire pressure is usually inspected whenever the driver feels that the tire pressure is insufficient or when a tire has been inflated and it is desired to determine if excessive or insufficient tire pressure conditions exist. The steps of attaching the tire pressure indicator to the inflating valve member and the viewing of the tire pressure reading requires adequate lighting and is thus inconvenient to execute under poor lighting conditions.